Such a protective cushion is stowed in the folded state along the lower roof edge within the vehicle. On account of the curved shape of the roof edge, the lower edge of the protective cushion must have a greater length than the straight connecting line between the two anchor points. When the protective cushion becomes activated, automatic shortening of its lower edge occurs due to the expansion of the protective cushion in transverse direction to the connecting line between the anchor points. In its activated state, the protective cushion is therefore stretched along its lower edge. However, after the gas pressure inside the protective cushion has decreased, the tension along its lower edge is lost. But in the event of the vehicle overturning, the protective action by the protective cushion is desired, by it acting as a protective curtain. The protective cushion cannot fulfill this function adequately when it is not under tension along its lower edge.